We have been seeking to define the role and mechanism of action of urinary immunoglobulins (Ig) especially secretory IgA, in protection from and resolution of recurrent urinary tract infections (UTI). The double antibody technique of urinary Ig quantitation has been developed. Urinary levels of IgA do not correlate directly with urinary antibacterial activity or the clinical course of children studied. Since secretory IgA has been correlated with bacterial adherence in the oral cavity, we are looking for a similar effect in the urinary bladder. Bacteria labelled with H3-leucine are injected into the lumen of the rat bladder, non-adherent bacteria are irrigated out after 2 hours, and adherent bacteria quantitated. A K antigen positive strain of E. coli shows a 5-10 fold increase in bladder bacterial adherence over (K antigen negative) controls. We plan to test the bacteria from children with UTI for adherence to rat bladder and correlate with K antigen content and urinary Ig. We will also look for inhibition of adherence by filter-sterilized urine. In addition, the adherence mechanism will be looked at by scanning electronmicroscopy.